The Evolution of Timekeeping
The passage of time has always been one of the human race’s central fascinations, and devising methods of measuring that passing has long been an obsession.
Where we are now is the result of a 20,000-year process of evolution, and we are by no means at the end.
But from the incredibly primitive to the mind-bogglingly complex, every timekeeping system has relied on some form of naturally occurring phenomena. Be it the course of the sun or the moon, the Earth’s gravity, the predictable vibrations of a crystal, all the way through to microwave or light energy, the precision of our devices has increased over the millennia to now unfathomable levels.
That accuracy is interwoven into all our lives, with everything from GPS navigation to power grids to financial networks depending on it.
Below we take a brief look at the history of timekeeping, and some of the major landmarks along the way.
A bone found in the Democratic Republic of the Congo may represent man’s very first efforts of tracking time. Dating back to around 18,000BCE, it is carved with hash marks thought to signify the passing of the days.
The next oldest example was unearthed in 2013, in Aberdeenshire, Scotland. A series of twelve moon-shaped pits, designed to perfectly align during the midwinter solstice, is believed to be the earliest attempt at a lunar calendar. Archaeologists estimate the pits are around 10,000 years old and so pre-date the examples found in Mesopotamia, once thought to be the first, by several thousand years.
It was the ancient Egyptians who first devised ways of dividing the day and night into equal sections. Originally recording the position of the shadow cast by a stick placed in the ground, by around 3,500BCE they had begun constructing huge obelisks to the Sun Gods. A series of markers on the ground enabled the Egyptians to track the time by the location of the obelisk’s shadow and even showed which season.
Knowledge of these sundials spread across the Mediterranean to the Greek, Roman and Persian empires.
Initially, the day was divided into 10 parts with a further four twilight hours, two each at dawn and sunset.
By 2100BCE, the Egyptians were separating the day and night into 12 hours (from the Greek word hora) but the actual period of an hour was not consistent. The length would vary by season as they were measured by the rising of certain stars in the night sky. As the days were of differing lengths depending on the time of year, the duration of an hour changed in relation.
While sun dials were effective during the day, and in good weather, they were obviously useless at night or in less sunny climates.
The next major advance in timekeeping was invented to overcome these limitations and came in the shape of the water clock.
Otherwise known as clepsydra, these too are thought to originate from ancient Egypt and work by measuring the flow of liquid into (or out from) a basin with hour lines inscribed on it.
There is evidence of water clocks being used in Babylon and Egypt in the 16thcentury BCE, although countries such as China and India also have their own examples from around the same era.
Other methods which worked without reliance on the sun involved falling sand in an hourglass or graduated candles—the candle burned lower and lower, and marked the passing of time. They were still being used in Japan up until the 10thcentury AD.
The First Clocks
The first recognizable mechanical clock was created in 723 A.D. by a Chinese Buddhist monk, mathematician and astronomer named I-Hsing. Named the ‘Water-Driven Spherical Birds-Eye View Map of The Heavens’it was an astronomical clock mounted at the top of a 30-foot tower and operated by dripping water. Constructed of iron and bronze, it chimed on the hour and sounded drum beats every quarter of an hour. Although it was the first of its kind it was not invented to tell the time perfectly, but rather to calculate when a royal baby was conceived. (How it would actually achieve this has been lost to the mists of history).
The design was improved upon in 976 A.D. when a fellow Chinese astronomer and mechanical engineer, Chang Ssu Hsiin, used mercury instead of water, which prevented the mechanism freezing in cold weather.
Although credit is often given to various Europeans, it was the Chinese that were at the forefront of the earliest mechanical breakthroughs. In 1090 during the Song Dynasty, an inventor named Su Sung produced another water-powered astronomical clock with, for the first time, an escapement mechanism as well as the earliest known endless power transmitting chain drive.
The verge escapement signified a huge development in timekeeping and was first seen sometime in 13thcentury Europe. Otherwise known as the crown wheel escapement, its invention marked the transition between measuring time through a continuous process, such as a flowing liquid, to oscillations, such as the swing of a pendulum.
Still enormous in size, they would be used in the clock towers of cathedrals or monasteries, and drove a forerunner to the modern balance wheel, called the foliot. The foliot was a horizontal bar that swung back and forth, and the rate of the clock could be controlled by altering the position of the weights at either end.
Still in use up until the 19thcentury, the verge escapement progressed so far, and their structure made so small, they were put to use inside pocket watches.
A Dutch physicist, astronomer and mathematician named Christiaan Huygens is the man perhaps most responsible for the timekeeping methods we know today. As well as perfecting the first pendulum clock in 1656, he was also the inventor of the modern oscillator—as in, a balance wheel and hairspring working together, which he came up with a few years later in 1675.
That oscillator is fed energy by the escapement which, in turn, sets the escapement’s rate of locking and unlocking the gear train.
Some three centuries later, it is still the basis for the vast majority of mechanical watches.
By the turn of the 19thcentury, both clocks and watches had reached a certain level of accuracy but remained expensive items reserved for the privileged few.
Manufacturers attempted to streamline mass-production in order to make their products more accessible to the everyman, and it was an American watchmaker by the name of A.L. Dennison who led the way. Teaming up with Edward Howard, a clockmaker from Roxbury, Mass., the two developed machinery to modernize the whole process, giving rise to the American Waltham Watch Company in the mid-1800s.
Yet up until the beginning of the Second World War, the wristwatch was very much seen as purely a lady’s accessory, while the pocket watch remained the reserve of gentlemen.
The utility of a watch worn on the wrist proved itself during wartime, and from the middle of the 20thcentury onwards, they became just about the only piece of jewelry a man would consistently wear. Their reputation was helped immeasurably by two revolutions from a young Swiss company by the name of Rolex. Perfecting, in quick succession, the waterproof Oyster case and the automatic self-winding mechanism, called the Perpetual, they transformed the image of the wristwatch, from delicate instrument to robust tool.
The Quest for Ever Greater Accuracy
Although mechanical watchmaking progressed at a rate of knots, winning more and more accolades for accuracy, there was always going to be a limit to just how precise springs and gears could be.
As early as 1928, the first experiments were taking place with electrified quartz crystals at Bell Laboratories in New York. They were found to vibrate at an extremely reliable frequency when a current was passed through them, leading to the development of the first quartz clocks. Installed at the Royal Observatory in London in 1939, they exhibited a variance of just two thousandths of a second/day. By the end of WWII, that was down to just one second every 30 years.
Quartz technology progressed fairly slowly, but by the 1960s the first watches emerged, leading to the utter decimation of the traditional industry in Switzerland. Known as the quartz crisis, it lasted up until the 1980s when the Swiss were able to launch a comeback with, ironically, their own quartz model—the Swatch. Cheap, disposable and fun, they sold in the millions, pouring much needed funds back into the country and saving the few mechanical manufacturers who still survived.
Accurate though the technology was however, it had itself already been superseded by 1948. The natural resonant frequency of a caesium atom was found to be even more uniform than that of a quartz crystal, as discovered by Harold Lyons of the National Bureau of Standards, Washington, D.C.
By 1955, the first caesium-beam atomic clock had been developed leading, a decade or so later, to a reclassification of how long a second was. Now, according to the General Conference of Weights and Measures 1967, a second had the duration of ‘9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom’. So now you know.
Today, caesium clocks strategically placed around the globe set Coordinated Universal Time, the accepted standard for regulating the time anywhere in the world, and have a variance of less than one nanosecond a day.
The Future of Timekeeping
Of course, for some, one nanosecond a day is just too much. The latest optical clocks work similarly to atomic clocks but use atoms that have a frequency around 100,000 times higher. It means they oscillate at about a quadrillion times a second, leading to an even greater accuracy and stability.
That unbelievable precision could lead to another reconsidering of the second, and give us even more exact GPS equipment, as well as advancing many areas of astronomy.
At present, the technical complexity of optical clocks has led to too much instability for them to be recognized as official timekeepers, but their rate of progress is dramatic. They could well take over as the sanctioned global standard sometime soon.
Time, as they say, will tell.